Adaptive energy absorbing device for a steering column

ABSTRACT

An energy absorbing device for a collapsible steering column of a vehicle is able to compensate for the severity of a crash and the weight of the driver to better manage the absorption of energy in a crash event. A housing has at least one fixed abutment surface, and at least one adjuster disposed in the housing for selective lateral slidable movement. At least one anvil is disposed adjacent an initial abutment surface of the adjuster in spaced relation to the fixed abutment surface of the housing in a first position of the anvil associated with high energy absorption. A plastically deformable strap is supported between the anvil and the housing. The adjuster slides out of the path of the anvil in a crash event in response to input of a control signal allowing the anvil to slide into contact with the fixed abutment surface of the housing to define a second position of the anvil associated with lower energy absorption.

TECHNICAL FIELD

This application relates generally to steering columns, and moreparticularly to adaptive energy absorbing devices for collapsiblesteering columns.

BACKGROUND OF THE INVENTION

Automotive steering column assemblies are often equipped with kineticenergy absorbing devices to reduce the likelihood of injury to anoperator in the event of collision. One such device employs aplastically deformable metal strap which is drawn across an anvil in acrash event during the collapse of the steering column to absorb some ofthe energy of collapse.

Typically, the anvil is fixed and thus there is little control over theperformance of the absorbing device.

SUMMARY OF THE INVENTION

An energy absorbing device for a collapsible steering column of avehicle comprises a housing having at least one fixed abutment surface.At least one adjuster having an initial abutment surface is disposed inthe housing for selective laterally slidable movement therein. At leastone anvil is disposed in the housing between a surface of the housingand the initial abutment surface of the adjuster defining a firstposition of the anvil. A plastically deformable strap is supported atleast in part between the anvil and the housing. The anvil has anarcuate mating surface engaging the strap restricting slidable movementtherebetween. A base portion of the anvil engages the initial abutmentsurface of the adjuster maintaining the base portion in spaced relationfrom the fixed abutment surface of the housing. The adjuster islaterally slidable in response to a signal in a crash condition of thevehicle removing the adjuster from between the anvil and the housing.The base portion of the anvil can then move from the first position intomating contact with the fixed abutment surface of the housing inresponse to an applied force from the strap defining a second positionof the anvil. The arcuate surface of the anvil has a first coefficientof friction against the strap while the anvil is in the first positionand a second coefficient of friction against the strap while the anvilis in the second position. The second coefficient of friction is lessthan the first coefficient of friction, thereby allowing the steeringcolumn to collapse under a lighter axial load while the anvil is in thesecond position.

One object of the invention is to provide an energy absorbing device fora collapsible steering column that compensates for the severity of avehicle crash and the size, weight and/or position of the driver.

The invention has the advantage of providing selectively slidable anvilswhich can move between different positions to vary the reaction path ofthe strap, and thereby control the energy absorption characteristics ofthe system.

One further advantage is that the system is of simple construction andis adaptable to many different crash conditions.

Other objects, features and advantages of the invention will become moreapparent in view of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a motor vehicle steering column havingan energy absorbing device constructed according to one embodiment ofthe invention;

FIG. 2 is an exploded perspective view of the energy absorbing device ofFIG. 1;

FIG. 3 is a partially assembled view of the energy absorbing device ofFIG. 2, but with a cover omitted;

FIG. 4 is an enlarged cross-sectional plan view of the energy absorbingdevice of FIG. 3 showing a pair of anvils in a first position;

FIG. 5 is a view like FIG. 4, but showing one of the anvils moved to asecond position; and

FIG. 6 is a view like FIG. 4, but showing both of the anvils moved to asecond position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An energy absorbing device constructed according to a presentlypreferred embodiment of the invention is shown generally at 10 in FIGS.1-6. The energy absorbing device 10 is shown for use in FIG. 1 with asteering column assembly 12 that includes a collapsible upper steeringcolumn jacket 14 relative to a lower bracket 16 generally along alongitudinal axis 15 of the assembly 12. In a crash condition of a motorvehicle (not shown) with another object, the vehicle body deceleratesmore rapidly than the operator (not shown) so that the operator isthrust against a hand wheel 18 of the motor vehicle. During impact, theenergy absorbing device 10 receives a signal from a transducer or sensor19 by way of an electrical connection to an electrical control module(ECM) or computer 21. The sensor 19 detects the operator's size orweight, position, etc. and relays the data to the onboard computer 21.The computer 21, in turn, generates a load curve using the data from thesensor for directing the energy absorbing device 10 to resist lineartranslation of the upper steering column jacket 14 to decelerate theoperator, while at the same time converting into work a fraction of theoperator's kinetic energy to reduce the potential harm to the operator.

The energy absorbing device 10 includes a housing 20 having a channel 22with a serpentine path. Within the channel 22, at least one andpreferably a pair of pockets 24, 26 are formed for receiving a pair ofanvils 28, 30 respectively. Each pocket 24, 26 has a fixed abutmentsurface 32, 34 providing a final stop surface for the anvils, 28, 30 ina collapsing condition of the steering column assembly 12.

The housing 20 has an adjuster pocket for each anvil, shown here as apair of adjustable pockets 36, 38 for receiving a pair of adjusters 40,42, respectively. Each adjuster pocket 36, 38 extends generallylaterally in relation to opposite sidewalls 46, 48 of the housing 20.The pockets 36, 38 preferably have a bottom or endsurface 45 withtapered sidewalls 44 extending generally laterally therefrom and taperedtoward one another so that they converge toward the side walls 46, 48.The tapered sidewalls 44 act to maintain the adjusters 40, 42 within thepockets 36, 38 upon lateral movement of the adjusters 40, 42 within thehousing 20. Preferably, a threaded opening 50 is formed in each end 52,54 of the housing 20 for receiving a pair of threaded fasteners 56 tomaintain the adjusters 40, 42 in their initial position. When in theirinitial position, the adjusters, 40, 42 present an initial abutmentsurface 58, 60 respectively, to maintain the anvils 28,30 in a firstposition.

The adjusters 40, 42 are assembled within the adjuster pockets 36, 38 sothat a bottom or end surface 47 of the adjusters 40, 42 preferably seatagainst the bottom surface 45 of the adjuster pockets 36, 38 to positionthe adjusters 40, 42 in their initial assembled position. When theadjusters, 40, 42 are maintained in their initial position, the initialabutment surfaces 58, 60 extend into the pockets 24, 26 to maintain theanvils 28, 30 in a spaced relation from the fixed abutment surfaces 32,34, respectively. The fasteners 56 are preferably threaded within thethreaded openings 50 to engage the adjusters 40, 42 and to inhibit theadjusters from unintentional slidable movement within the adjusterpockets 36, 38. To facilitate laterally slidable movement of theadjusters 40, 42 within the adjuster pockets 36, 38, preferably theadjusters 40, 42 have an explosive charge therein.

The anvils 28, 30 are inserted into the pockets 24, 26 with each anvil28, 30 having an arcuate mating surface 62 with a base portion 64generally opposite thereto. When inserted into the pockets 24, 26, andinto their first position, the base portions 64 engage or abut theinitial abutment surfaces 58, 60 of the adjusters, 40, 42 and are spacedfrom the fixed abutment surface 32, 34 of the housing 20. With theanvils 28, 30 in their first position, the channel 22 extends around thearcuate mating surfaces 62, thereby forming the serpentine path in whicha plastically formable metal strap 66 is routed, such that the strap 66takes on a generally S-shaped configuration as shown in the drawings.

The strap 66, with the anvils 28, 30 in their first position, wrapsaround the arcuate mating surfaces 62 of the anvils 28, 30 apredetermined number of degrees to restrict the slidable movementbetween the strap 66 and the anvils 28, 30. The strap 66 preferably hasan opening 68 adjacent one of its ends for fastening the strap 66 to afixed support 70 of the vehicle. A fastener 72 is shown fastening thestrap 66 to the fixed support 70 to statically maintain the strap in itsgenerally fixed position throughout a collapsing cycle of the steeringcolumn assembly 12.

To complete the assembly of the energy absorbing device 10, a cover 74is fastened to the housing 20 preferably by way of a pair of fasteners75 that pass through a pair of openings 77 in the upper steering columnjacket 14, through a pair of fastener openings 76 in the cover 14 andinto a pair of threaded openings 78 within the housing 20. As such, thefasteners 75 both attach the housing to the upper steering column jacket14 and secure the cover 74 to the housing 20. The cover 74 preferablyhas a pair of openings 80 allowing the emission of gas from the pockets36, 38 upon ignition or detonation of the explosive within of theadjusters 40, 42.

At the time of a crash or head-on collision in which the steering columnassembly 12 collapses, conditions such as vehicle speed, driver seatposition, driver weight or size, etc. are monitored by the sensor 19 anda signal is sent to the vehicle body computer 21 to generate an optimalload curve value to actuate or detonate the adjusters 40, 42. Dependingon the results of the load curve value, either one or both of theadjusters 40, 42 detonate, thereby emitting a gas such that therespective adjusters 40, 42 travel laterally outwardly within the adjustpockets 36, 38. As such, the initial abutment surfaces 58, 60 areremoved from between the anvils 28, 30 and the fixed abutment surfaces32, 34. As a result, the anvils 28, 30 move from the first position intomating contact with the fixed abutment surfaces 32, 34 in response to anapplied force from the metal strap 66 defining a second position of theanvils 28, 30.

Upon movement of the anvils 28, 30 from their first position to theirsecond position, a first coefficient of friction between the arcuatemating surfaces 62 of the anvils 28, 30 and the strap 66 is reduced to asecond coefficient of friction, thus allowing the steering columnassembly 12 to collapse under a lighter axial load (i.e., with lessresistance to deformation).

As shown in FIG. 5, when one of the anvils 28 moves from its firstposition to its second position, the strap 66 moves from a more severeS-shaped configuration to a less severe S-shaped configuration. As aresult, the predetermined number of degrees of wrap of the strap 66about the arcuate mating surfaces 62 is altered to a lesserpredetermined number of degrees of wrap when the anvil 28 is seatedagainst the fixed abutment surface 32 and in its second position.Further yet, as seen in FIG. 6, when both anvils 28, 30 move from theirfirst positions to their second positions, the strap 66 takes on an evenless severe S-shaped configuration, and thus the number of degrees ofwrap of the strap 66 about the arcuate mating surfaces 62 is furtherreduced. As a result, the predetermined number of degrees of wrap of thestrap 66 about the arcuate mating surfaces 62 while the anvils 28, 30are in their first position is greater than the predetermined degrees ofwrap of the strap 66 about the arcuate mating surfaces 62 while theanvils 28, 30 are in their second position. With fewer degrees of wrapof the strap 66 about the arcuate mating surfaces 62, the coefficient offriction between the strap 66 and the arcuate mating surfaces 62 isreduced. This allows the housing 20 of the energy absorbing device 10 toslide relative to the plastically deformable strap 66 under a lighterapplied axial load along the longitudinal axis 15 of the steering columnassembly 12.

It should be recognized, that the movement of one or both of the anvils28, 30 from their first position to their second position is dependentupon the signal received from the ECM to the adjusters 40, 42. Ifconditions warrant a more resistant system to collapsing of the steeringcolumn assembly 12, then only one of the adjusters 40, 42 will igniteand move laterally within the respective adjuster pocket 36, 38.However, if conditions warrant a more compliant system, then bothadjusters 40, 42 will ignite to move laterally within the adjusterpockets 36, 38. Either way, upon removal of one or more of the adjusters40, 42 from between the anvils 28, 30 and the fixed abutment surfaces32, 34, the anvils 28, 30, upon being forced by the strap 66 to move totheir second position, move generally away from one another toward theirrespective fixed abutment surfaces 32, 34.

It should be recognized that although the adjusters 40, 42 arerepresented here as having an explosive charge, the adjusters 40, 42could comprise other mechanisms to facilitate lateral movement of theadjusters within the pockets 36, 38, such as solenoids or the like.

Obviously, many modifications and variation of the present invention arepossible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. The inventionis defined by the claims.

1. An energy absorbing device for a collapsible steering column of avehicle, comprising: a housing having at least one fixed abutmentsurface; at least one adjuster disposed in said housing for selectivelaterally slidable movement therein and having an initial abutmentsurface, said adjuster further comprising an explosive device emitting agas in response to a signal in a crash condition of the vehicle toundertake said selective laterally slidable movement; at least one anvilhaving a mating arcuate surface, said anvil being disposed in saidhousing abutting said initial abutment surface of said adjuster andspaced longitudinally from said fixed abutment surface in a firstposition of said anvil; a plastically deformable strap supported andconfigured in a generally S-shaped pattern between said anvil arcuatemating surface and said housing; and said anvil arcuate mating surfaceengaging said strap so as to restrict slidable movement therebetween andhaving a base portion for engaging said initial abutment surface of saidadjuster maintaining said base portion in spaced relation from saidfixed abutment surface of said housing and said adjuster being laterallyslidable in response to said signal in a crash condition of the vehicleso as to remove said adjuster from between said anvil and said housingallowing said base portion of said anvil to move from said firstposition into mating contact with said fixed abutment surface of saidhousing in response to an applied force from said strap defining asecond position of said anvil, said arcuate surface of said anvil havinga first coefficient of friction with said strap while said anvil is insaid first position and said arcuate surface having a second coefficientof friction with said strap while said anvil is in said second position,said second coefficient of friction being less than said firstcoefficient of friction allowing the steering column to collapse under alighter axial load while said anvil is in said second position. 2.(cancelled)
 3. (cancelled)